Disassembled truck(Bogie) of a WDP/G-4 loco at the training center. The entire weight of the super structure rests on the Load pads, 4 per truck. Load Pads are also called as Secondary Suspension. Note that the load pads are flexible and made of hard rubber and probably reinforced with steel rings. This flexibility allows for the truck to turn on curves and also provides additional cushioning between the truck and the super structure. The function of the center pivot is to act as a pivot for the truck to turn and to transfer the tractive force from the truck to the super structure. Note that the tractive forces are not transferred via load pads. Better riding comfort of WDP/G-4 locos can be attributed to this design feature. This is unlike the Alco design of WDM-2 where both the weight of the super structure and tractive forces are transmitted entirely via the center pivot. And there is no cushioning between the truck and the super structure. This results in the rough ride of WDM-2 class of locos.